Field of the Invention
The present invention relates to devices for measuring the amount of ultraviolet light used in treating a subject, and is more particularly concerned with a device for monitoring the total amount of ultraviolet light energy applied to the subject during a period of time during which the intensity of the energy may vary, and to sound a warning either audible or visible to warn the subject that the predetermined amount of energy has been applied to him.
Description of the Prior Art
Ultraviolet light therapy utilizing light either from the sun or from ultraviolet lamps has long been used both for applying a tan to the skin of a subject and for treating the skin of the subject for certain diseases for which ultraviolet light has therapeutic value. In order to control the total amount of ultraviolet light energy received by the subject, a standard timer has been conventionally used which, after a predetermined period, provides an alarm, turns off the lamps, or both.
More recently it has been found that the physiological effect of ultraviolet light may be greatly accelerated if the subject is first administered certain drugs prior to the ultraviolet light exposure. The drugs are administered either topically or internally. This prior treatment permits a given degree of physiological treatment to be applied in a far shorter time that when ultraviolet light is applied in the absence of such drugs. Among such drugs are those developed for treating psoriasis. Among these drugs is Psoralen, manufactured and marketed by the Paul B. Elder Company. When the subject is thus first sensitized, it is extremely important in administering ultraviolet radiation that the amount of radiation energy received by the subject be very carefully controlled within certain limits to prevent over exposure and its attendant injury. The use of timers alone may not provide the necessary precision of total ultraviolet light energy measurement, since the intensity of sunlight may vary with increased or decreased cloud coverage, and time of day. The intensity of light produced by ultraviolet lamps may vary with the age of the lamps and with changes in the voltage of the electrical main.